Air injection engine

ABSTRACT

An internal combustion engine of the present invention features separate compression and expansion cycles. The engine includes a separate compressor device which pressurizes air by a ratio greater than 15 to 1, at least one two stroke combustion cylinder and a compressed air conduit for transferring compressed air from the compressor to the at least one combustion cylinder. An air injection valve injects the compressed air into the combustion cylinder during the second half portion of the return stroke of the combustion cylinder. The compressed air is mixed with fuel and combusted for expansion during a power stroke. In this engine compression occurs only to a minor degree in the combustion cylinder. Accordingly, the compression ratio of the present engine may be significantly higher or lower than the volumetric expansion ratio of the combustion cylinder thus resulting in corresponding increases in either power density or thermodynamic efficiency respectively.

This application is a continuation of application Ser. No. 11/349,627which was filed Feb. 8, 2006.

U.S. application Ser. No. 11/349,627 a continuation of application Ser.No. 10/777,796 which was filed Feb. 12, 2004.

U.S. application Ser. No. 10/777,796 claimed the benefit of U.S.Provisional Patent Application No. 60/446,934 filed Feb. 12, 2003.

FIELD OF THE INVENTION

The present invention relates to an internal combustion engine.

BACKGROUND OF THE INVENTION

Many types of internal combustion engines are known in the art. It iswell known that increasing the compression ratio of an internalcombustion engine will result in increased thermodynamic efficiency.With many prior art engines, the compression ratio of the engine islimited by the expansion ratio of the cylinders of the engine. In otherprior art engines, the compression ratio of the engine is limited to arelatively low value because auto-ignition of the fuel air mixture willoccur too early in the cycle as compressed air reaches a temperatureabove the auto-ignition temperature of the fuel.

BRIEF DESCRIPTION OF THE INVENTION

In an embodiment of the present invention the aforementioned problemsare addressed by providing an internal combustion engine in which thecompression and expansion portions of the engine's cycle and thecompression and expansion ratios are independent. The present engineincludes a compressor which pressurizes air by a ratio which may besubstantially more than 15 to 1, a combustion cylinder including areciprocating piston which oscillates between a top dead center positionand a bottom dead center position in a power stroke and between thebottom dead center position and the top dead center position in a returnstroke and a compressed air conduit for transferring compressed air fromthe compressor to the combustion cylinder. Pneumatic communicationbetween the compressed air conduit and the combustion cylinder isgoverned by a timed valve which intermittently opens to releasepressurized air into the combustion cylinder when the piston is in thesecond half portion of the return stroke. A fuel injector is employed tomix fuel with the pressurized air to make a fuel—air mixture which iscombusted to produce hot, high pressure gaseous combustion productswhich expand during the power stroke. In this present engine, becausethe compression of air for use in the combustion portion of the cycle isconducted separately and then injected or released into the combustioncylinder when it is needed, the ratio of compression can besignificantly higher or lower than the ratio of expansion. A higherexpansion ratio results in a significant increase in thermodynamicefficiency while a higher compression ratio results in a significantincrease in power density. Moreover, since the present engine conductscompression and expansion separately, compressed air for use in thecombustion cylinder may be cooled to prevent early ignition of a fuelair mixture thus permitting a higher compression ratio.

The injection of pressurized air from the compressed air conduit intothe combustion cylinder preferably occurs during a relatively smallportion of the combustion cylinder cycle preferably when the piston isin the second half of the return stroke. Accordingly, a timed valve suchas an indexed rotary valve which presents a relatively large flow areamay be used to provide timed intermittent pneumatic communicationbetween the compressed air conduit and the combustion cylinder. Such avalve arrangement should therefore provide timed, intermittent pneumaticcommunication between the compressed air conduit and the combustioncylinder sufficient to allow air pressure in the compressed air conduitand the combustion chamber to substantially equalize during a relativelysmall portion of the combustion cylinder cycle when the piston of thecombustion cylinder is in the second half of the return stroke.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the internal combustion engine of the presentinvention.

FIG. 1A is a diagram of an embodiment of the internal combustion engineof the present invention having three combustion cylinders and twocompression cylinders.

FIG. 2A shows the compression cylinder during its intake stroke.

FIG. 2B shows the compression cylinder at bottom dead center.

FIG. 2C shows the compression cylinder during its compression stroke.

FIG. 3 is a timing diagram showing the timing of segments A-G of thecombustion cylinder cycle shown in FIG. 3A-FIG. 3H and the combustioncylinder cycle shown in FIGS. 4A-4H.

FIG. 3A shows the combustion cylinder during cycle segment A as gaseouscombustion products remaining from a previous cycle are being expelledthrough the exhaust valve.

FIG. 3B shows the combustion cylinder during cycle segment where A andB2 overlap when the pressurized air injection valve and the exhaustvalve are both open in order to scavenge the last remaining gaseouscombustion products from the previous cycle.

FIG. 3C shows the combustion cylinder during cycle segment B2 aspressurized air is being injected into the combustion cylinder.

FIG. 3D shows the combustion cylinder during cycle segment C as fuel isbeing injected into the combustion cylinder.

FIG. 3E shows the combustion cylinder during cycle point D where thecombustion piston is near top dead center and the fuel air mixture isbeing ignited by a spark plug.

FIG. 3F shows the combustion cylinder during cycle segment E where thecombustion piston is at top dead center as the fuel air mixture is inthe process of combustion.

FIG. 3G shows the combustion cylinder during cycle segment F during thepower stroke as combustion product gases are expanding.

FIG. 3H shows the combustion cylinder during optional cycle segment Gwhere the combustion piston is at bottom dead center as gaseouscombustion products escape through the exposed exhaust port.

FIG. 3I is an isometric view of the combustion cylinder with an indexedrotary valve.

FIG. 3J is an cross sectional view showing a cross section of the valvehousing, the valve body and the combustion cylinder generally taken fromplane A-A of FIG. 3I except with the valve body in the position shown inFIG. 3L

FIG. 3K is an isometric view of the indexed rotary valve with the valvehousing removed for clarity as the valve body comes to rest at the endof a 90 degree rotation.

FIG. 3L is an isometric view of the indexed rotary valve with the valvehousing removed for clarity as the valve body begins a next 90 rotation.

FIG. 3M is an isometric view of the indexed rotary valve with the valvehousing removed for clarity as the valve body is rotating at a highspeed.

FIG. 3N is an isometric view of the indexed rotary valve with the valvehousing removed for clarity as the valve body comes to rest at the endof a 90 degree rotation.

FIG. 3P is an plot showing valve body rotational velocity as a functionof crankshaft position for the indexed rotary valve arrangement shown inFIGS. 3I-3N.

FIG. 4A shows the combustion cylinder including a rotary injection valveduring cycle segment A as gaseous combustion products remaining from aprevious cycle are being expelled through the exhaust valve.

FIG. 4B shows the combustion cylinder including a rotary injection valveduring cycle portion where A and B2 overlap when the pressurized airinjection valve and the exhaust valve are both open in order to scavengethe last remaining gaseous combustion products from the previous cycle.

FIG. 4C shows the combustion cylinder including a rotary injection valveduring cycle segment B2 as pressurized air is being injected into thecombustion cylinder.

FIG. 4D shows the combustion cylinder including a rotary injection valveduring cycle segment C as fuel is being injected into the combustioncylinder.

FIG. 4E shows the combustion cylinder including a rotary injection valveduring cycle point D where the combustion piston is near top dead centerand the fuel air mixture is being ignited by a spark plug.

FIG. 4F shows the combustion cylinder including a rotary injection valveduring cycle segment E where the combustion piston is at top dead centeras the fuel air mixture is in the process of combustion.

FIG. 4G shows the combustion cylinder during cycle segment F during thepower stroke as combustion product gases are expanding.

FIG. 4H shows the combustion cylinder during optional cycle segment Gwhere the combustion piston is at bottom dead center as gaseouscombustion products escape through the exposed exhaust port.

FIG. 5 is a Pressure verses Specific Volume graph for the thermodynamiccycle of the of an embodiment of the invention internal combustionengine having an inter-cooler for cooling pressurized air.

FIG. 6 is a Temperature versus Entropy graph for the thermodynamic cycleof the of an embodiment of the invention internal combustion enginehaving an inter-cooler for cooling pressurized air.

FIG. 7 is an illustrative plot of Power versus Compression Ratio forcurves of a set value for Expansion Ratio.

FIG. 8 is an illustrative plot of Thermodynamic Efficiency versusCompression Ratio for curves of a set value for Expansion Ratio.

DETAILED DESCRIPTION

Referring to the drawings, FIG. 1 illustrates an internal combustionengine 10 in accordance with an embodiment of the invention. In FIG. 1,an internal combustion engine 10 is shown including compressor 12,compressed air conduit 50 and combustion cylinder 70. Combustioncylinder 70 includes a cylinder 74 and a reciprocating piston 76 whichis one of the mechanical arrangements for defining an internalcombustion engine which features a combustion chamber that cyclesbetween a minimum volume and a maximum volume. Combustion cylinder 70may be one of two or more combustion cylinders coupled together on acommon crankshaft 76D. Likewise compressor 12 may include a compressioncylinder 13 as shown in FIG. 1. Compressor 12 provides compressed air tocompressed air conduit 50. Together, compressor 12 and compressed airconduit 50 provide a source of compressed air for use by combustioncylinder 70.

FIG. 1A schematically presents an example embodiment of the presentengine 10A having three combustion cylinders 70 associated on commoncrankshaft 76D and a compressor 12 comprising two compression cylinders13 associated on a common compressor crankshaft 18D. In FIG. 1A,crankshaft 76D and compressor crankshaft 18D are coupled by a variableratio gear box 12A. This variable ratio gear box may be adjusted toadjust the volume of compressed air delivered to compressed air conduit50. The advantage of having a the capability to control the delivery ofthe compressed air within conduit 50 are described in detail below butgenerally allow an adjustment in operating conditions between a modehaving a relatively low volumetric compression ratio and a relativelyhigh expansion ratio for maximum thermodynamic efficiency and a mode ofrelatively high volumetric compression ratio and a relatively lowexpansion ratio for maximum power density. The combustion cylinders 70of example engine 10A each include injection valves 72A, exhaust valves72B, fuel injectors 72C and ignition initiators 72D. FIG. 1A alsoillustrates a timing system 300 for timing the operations of injectionvalves 72A, exhaust valves 72B, fuel injectors 72C and ignitioninitiators 72D. Such a timing system is needed for the operation of aninternal combustion engine but is omitted from many of the other figuresfor clarity. Timing system 300, in this example, includes a cam shaft302, a fuel injection timer 304 and an ignition timer 306. Cam shaft 302is mechanically coupled to crankshaft 76D and carries a series ofeccentric cams for governing the operations of injection valves 72A andexhaust valves 72B. Fuel injection timer 304 governs the operations offuel injectors 72C, while ignition timer 306 governs the operations ofignition initiators 72D. Both fuel injection timer 304 and ignitiontimer 306 are coupled to crankshaft 76D. Timing system 300 as presentedhere is only one of many possible timing systems and the selection hereof particular types of components is not intended to limit the scope ofthe invention. FIG. 1A also illustrates that combustion cylinder 70 maybe one of a plurality combustion cylinders coupled by a commoncrankshaft. FIG. 1A is not intended to suggest that compressor 12 mustbe a cylinder—piston type compressor or that compressor 12 would belimited to having two compression cylinders.

Compressor 12 takes in air from the outside environment and deliverscompressed air to compressed air conduit 50. In the embodiment shown inFIG. 1, compressor 12 is a compression cylinder 13 which furtherincludes a compression cylinder head 14, a compression cylinder body 16and a compression piston 18. The upper surface of compression piston 18,the inside wall of compression cylinder body 16 and compression cylinderhead 14 define compression chamber 16A which constantly changes involume as compression piston reciprocates with compression cylinder 13.Compression piston 18 is connected by a connecting rod 18C to acompression crankshaft 18D. Compression cylinder head 14 includes anintake valve 14A and an outlet valve 14D. Intake valve 14A governspneumatic communication between an intake port 14B leading to theoutside environment and compression chamber 16A. Outlet valve 14Dgoverns pneumatic communication between compression chamber 16A and anoutlet port 14E which leads to compressed air conduit 50.

Compressed air conduit 50 retains compressed air produced by compressor12 and conveys compressed air to combustion cylinder 70. In theembodiment shown in FIG. 1, compressed air conduit 50 generally includesa storage means and a cooling means so that a supply of temperatureconditioned pressurized air may be available for use by combustioncylinder 70. In the embodiment shown in FIG. 1, compressed air conduit50 further includes an intake portion 52, an insulated reservoir 54, aheat rejecting portion 56 having heat rejecting fins 56A, a coolcompressed air valve 60, an insulated hot air conduit 54A, hotcompressed air valve 62, a pressure regulator 64 and an outlet portion66. Cool compressed air valve 60 and hot compressed air valve 62 can beadjusted in order to adjust the temperature of air in outlet portion 66as will be described in more detail below. Pressure regulator 64 is forregulating the pressure of the pressurized air in outlet portion 66.Preferably, reservoir 54 should encompass a volume sufficient to providea steady supply of compressed air for use by combustion cylinder 70.

Combustion cylinder 70 receives compressed air from compressed airconduit 50 as well as fuel which is mixed with the compressed air forcombustion and expansion in a power stroke. In the embodiment shown inFIG. 1, combustion cylinder 70 is a two stroke cylinder having a pistonwhich oscillates in a cycle including a power stroke in which the pistonmoves from a top dead center position to a bottom dead center positionand a return stroke in which the piston moves from the bottom deadcenter position to the top dead center position. Generally, theinjection of compressed air from compressed air conduit 50 intocombustion cylinder 70 is timed to occur during a relatively shortportion of the cycle when the piston is in the second half of the returnstroke. Also generally, the injection of fuel into combustion cylinder70 is preferably timed to occur after the injection of compressed airhas begun. The combustion of the fuel air mixture preferably occursafter the injection of compressed air and fuel and preferably notsubstantially prior to the piston reaching top dead center. In theembodiment shown in FIG. 1, combustion cylinder 70 further includes acombustion cylinder head 72, a combustion cylinder body 74 and acombustion piston 76 having an upper piston surface 76A. A connectingrod 76C links combustion piston 76 to an associated crankshaft 76D forthe conversion of the reciprocating motion of the piston into rotationalpower at the crankshaft 76D. Combustion cylinder body 74 includes acylindrical inside wall 74A which may be penetrated by an optionalexhaust port 74C. Exhaust port 74C and exhaust valve 72B are examples oftypical devices or means employed for releasing exhaust from acombustion chamber. Combustion cylinder head 72 further includes aninjection valve 72A, an exhaust valve 72B, a fuel injector 72C and mayalso include an ignition initiator 72D which in FIG. 1 is shown as aspark plug. Combustion cylinder 70 may optionally be arranged as aDiesel cylinder which compresses a mixture of air and fuel to asufficient pressure to cause auto ignition of the mixture. As a Dieselcylinder, combustion cylinder 70 would not need ignition initiator 72D.Combustion cylinder head 72, inside wall 74A of cylinder body 74 andupper piston surface 76A define a combustion chamber 74B whichconstantly changes in volume as piston 76 moves between a bottom deadcenter position as shown in FIG. 3H or 4H and a top dead center whichwould appear to be half way between the positions shown in FIGS. 3E and3F or FIGS. 4E and 4F.

FIG. 1 illustrates combustion cylinder 70 such that pressurized airvalve 72A is a conventional stem valve. FIGS. 3A-3H illustrate theoperation of power cylinder 70 with a conventional stem valve. With atypical prior art engine, a stem valve for regulating air intake may beopen during a relatively large portion of crankshaft cycle correspondingto approximately 180 degrees of crankshaft rotation. With the presentengine, a pressurized air valve 72A may be open during a relativelysmall portion of the crankshaft cycle corresponding to 10 to 15 degreesof the crankshaft rotation. Because of the mechanical characteristics ofstem valves, the actuation of a stem valve for such a small portion ofthe crankshaft cycle may limit the operating RPM of power cylinder 70.Accordingly, in order to achieve higher RPMs, it would be preferable toemploy a valve arrangement capable of substantially equalizing thepressure between the pressurized portion of the system such as outletportion 66 of compressed air conduit 50 and combustion chamber 74Bduring a relatively small portion of the crankshaft cycle. FIGS. 3J-3Nillustrate an indexed rotary valve 82 adapted for filling combustionchamber 74B with pressurized air during a relatively small portion ofthe cycle. Also shown in FIG. 3I is an example timing system 300 whichincludes a timing chain 300B coupled to crankshaft 76D for driving a camshaft 302 for actuating exhaust valve 72B, a timing sensor 300Aassociated with drive wheel 92 of rotary valve 82 which is also drivenby timing chain 300B and a timing unit 305 which receives input fromtiming sensor 300A for controlling the timing of fuel injector 72C andignition initiator 72D.

As can be seen with reference to FIG. 3I, rotary valve 82 generallyincludes a valve portion 84 and an indexing portion 90. Valve portion 84is mounted to power cylinder 70 as shown in FIG. 3I. Valve portion 84may be best understood by referring to FIGS. 3J-3M. The cross sectionview of FIG. 3J is taken from plane A-A of FIG. 3I, except that valvebody 88 in FIG. 3J is rotated to a position corresponding to that shownin FIG. 3M. As can be best seen in FIG. 3J, valve portion 84 includes avalve housing 86 which rotatably carries a valve body 88. Valve body 88includes two intersecting passages 88A of generally oval cross-sectionwhich are arranged at right angles with respect to each other. Valvehousing 86 has a compatible longitudinal bore 86A for carrying valvebody 88 as well as bearings adapted for high speed rotation of valvebody. Valve housing 86 includes a pressurized air conduit opening 86Bwhich opens up to a generally oval shaped inlet port 86C. Inlet port 86Cmay be generally shaped to match the shape of passages 88A of valve body88. However, inlet port 86C is preferably not sealed against valve body88 so that passages 88A are constantly in communication with thepressurized volume inside housing 86 and thus outlet portion 66 ofpressurized conduit 50. This constant pressurization of passages 88Aoccurs regardless of their rotational position within valve housing 86.Valve housing 86 includes an oval shaped injection port 86D which isoval shaped to match the shape of passages 88A. However, unlike inletport 86C, injection port 86D is sealed between valve body 88 and theconstantly pressurized internal volume of valve housing 86 by aninjection seal 88E. A second housing seal 88F seals the pressurizedinternal volume of valve housing 86 and passages 88A from the outsideenvironment. The above described compatible ports and passages arepreferably shaped to maximize pneumatic communication between thepressurized portion of the system and combustion chamber 74B.

The purpose of indexing portion 90 is to cause the intermittent (or“indexed”) 90 degree rotation of valve body 88 during a 90 degreeportion of a complete cycle of constantly rotating crankshaft 76D.Indexing portion 90 includes a drive wheel 92 mechanically coupled tocrankshaft 76D for constant rotation and an index wheel 94 mechanicallycoupled to valve body 88 for intermittent, indexed rotation. Drive wheel92 includes a cog 92A and a retaining disc 92B having a scallopedportion 92C and a non-scalloped circular retaining portion 92D. Indexwheel 94 includes slots 94A for receiving cog 92A and external scallops94B for receiving non-scalloped retaining portion 92D of retaining disc92B. FIGS. 3K-3N illustrate the relative motions of continuouslyrotating drive wheel 92 and intermittently rotating index wheel 94.Valve housing 86 has been removed in FIGS. 3K-3N for clarity. In FIG.3K, drive wheel 92 is beginning a period of rotation in which it rotatesclockwise for 270 degrees while index wheel 94 remains stationary in aposition that blocks communication between inlet passage 86C andcombustion cylinder 70. In FIG. 3L, cog 92A of drive wheel 92 hastraveled clockwise 270 degrees and begins to engage slot 94A of indexwheel 94 thus causing index wheel 94 to begin rotating in a counterclockwise direction. In FIG. 3M, index wheel 94 is rotating at a highspeed relative to crankshaft 76D and drive wheel 92. The relativepositions of valve body 88 and valve housing 84 illustrated in FIG. 3Mare also shown in the cross sectional view of FIG. 3J. In FIG. 3N, indexwheel 94 has advanced 90 degrees from the position shown in FIG. 3M andis again stationary while continuously rotating drive wheel 92 hasreturned to the position shown in FIG. 3K. FIG. 3P provides plot whichinterrelates the rotational velocity of crankshaft 76D, which isconstant, and the rotational velocity of valve body 88 which variesgreatly during a 90 degree portion of the crankshaft cycle. Themechanism described here for driving the rotary valve is commonly knownas a Geneva wheel mechanism and is only one of many possible ways toaccomplish the above stated objective, which is, to open communicationbetween a pressurized volume and combustion chamber 74B in a rapid andintermittent manner during a relatively small portion of the crankshaftcycle and to open such communication sufficiently to allow thesubstantial equalization of air pressure between the pressurized volumeof the system and the combustion chamber

FIG. 1 shows compression cylinder 13 almost half way through an intakestroke and combustion cylinder 70 at the beginning of the second half ofthe return stroke. However, these relative positions are not intended toimply a relationship between the two cylinders. In FIG. 1, no directmechanical connection is shown between compression cylinder 13 andcombustion cylinder 70. Compression cylinder 13 and combustion cylinder70 can be coupled by a common crankshaft or could be coupled such theyoperate at substantially different speeds. The applicant intendshowever, that a portion of the power derived from the operation ofcombustion cylinder 70 be used to power compressor 12.

FIG. 1 illustrates compression cylinder 13 and combustion cylinder 70 asif they would be equivalent in quantity, size and shape. This wouldprobably not be the case.

FIGS. 2A-2C illustrate the operation of compression cylinder 13. FIG. 2Ashows compression cylinder 13 during its intake stroke. In FIG. 2A,intake valve 14A is open, outlet valve 14B is closed and compressionpiston 18 is descending as air is pulled into compression chamber 16A.In FIG. 2B, compression cylinder is at bottom dead center and intakevalve 14A and outlet valve 14B are both closed. In FIG. 2C, intake valve14A is closed and outlet valve 14B is open as the ascending compressionpiston 18 is forcing compressed air into intake portion 52 of compressedair conduit 50. This positive displacement compressor shown in FIG. 1and FIGS. 2A-2C is of a type that is well know in the art. However, itcould be replaced by any suitable compressor means that is capable ofdelivering compressed air with a compression ratio above 15 to 1.

Compressed air conduit 50 is intended to receive and store compressedair and then deliver it to combustion cylinder 70 within desiredtemperature and pressure ranges. Compression cylinder 13 as shown inFIG. 2A is intended to compress air at a ratio substantially in excessof 15 to 1. It should be noted that air at an ambient temperature andpressures (such as 20° C. and one atmosphere of pressure), whencompressed at 15 to 1, will increase in temperature to a temperaturethat may be above the auto-ignition temperature of a desired fuel.Accordingly, compressed air conduit 50 includes a heat rejecting portion56A having heat rejecting fins 56A for rejecting a portion of the heatpresent in the compressed air leaving compression cylinder 13. On theother hand, insulated reservoir 54 of compressed air 50 storescompressed air with minimal heat loss. Cool compressed air valve 60 andhot compressed air valve 62 for adjusting the flow through a hot conduit54A can be adjusted to mix an air stream that is controlled within apre-selected temperature range that is below the auto-ignitiontemperature of a desired fuel. The presence of this temperature controlfeature is merely a preferred feature for use with an engine that isintended for burning fuels subject to auto-ignition. In the alternative,this temperature control feature may be useful even where prematureauto-ignition is not an issue.

FIG. 3A-3H diagram the operation of combustion cylinder 70. FIGS. 4A-4Hdiagram the operation of combustion cylinder 70 with a rotary valve 82as shown in FIGS. 3I-3N instead of a stem type injection valve 72A. FIG.3 provides a corresponding timing diagram which shows the relativetiming of the positions shown in FIGS. 3A-3H and FIGS. 4A-4H. The timingdiagram of FIG. 3 can be envisioned as being divided into segments whichmay overlap. These segments further correspond to the variousconfigurations shown in the other figures including FIGS. 3A-3P andFIGS. 4A-4H. Segment A corresponds to FIGS. 3A and 4A to the extent thatvalve 72B of FIGS. 3A and 4A are open during segment A, yet segment Aalso corresponds to a relatively large portion of the crankshaft cyclewhereas FIGS. 3A and 4A only show piston 76 and connecting rod 76C inone position rather than a range of positions. During this segment,exhaust gasses are expelled from combustion cylinder 70 as piston 76executes a portion of its return stroke. Segment B1 in FIG. 3corresponds to the intermittent rotation of valve body 88 of indexedrotary valve 82 and is only applicable to the rotary valve configurationillustrated in FIGS. 3I-3N and FIGS. 4A-4H. Segment B2 is preferablycentered in segment B1. Segment B2 corresponds to the portion of thecycle in which one of passages 88A of valve body 88 is in communicationwith injection port 86D of valve housing 86 thus providing opencommunication between valve housing 86 (and thus by extension compressedair conduit 50) and combustion chamber 74B. In the rotary valve case,the center of segment B2 corresponds with the alignment of one ofpassages 88A with injection port 86D as illustrated in FIG. 3J. Yet, forthe stem valve case, segment B2 also corresponds to the portion of thecycle when injection valve 72A is open. Note that segment A and segmentB2 slightly overlap indicating the scavenging of exhaust gasses fromcombustion chamber 74B. Such scavenging is illustrated in FIGS. 3B and4B. If a simple stem valve is used for an injection valve, then segmentB1 is omitted and the overlapping portion of segment A and segment B2would correspond to FIG. 3B. Again, if a stem type injection valve isused, then the portion of segment B2 not overlapping with segment Awould correspond to FIG. 3C where pressurized air is being injected intocombustion cylinder 70. Segment C corresponds to the injection of fuelshown in FIGS. 3D and 4D. Location D corresponds to the activation of anignition initiator or spark plug as shown in FIGS. 3E and 4E. As hasbeen noted above location D as well as ignition initiator 72D areoptional and may be omitted if a Diesel type engine is desired. Fuelinjection of segment C of FIG. 3 may overlap or fall completely withinthe air injection portion B2 as desired by the engine designer. Thoseskilled in the art of engine design should appreciate that both airinjection portion B2 and fuel injection portion C should be completedprior to the action of ignition initiator 72D or in the case of aDiesel, the air injection should be complete prior to fuel injectionwhich will result in auto-ignition. Since the combustion piston 76 istraveling upward towards the top dead center position during thesesegments of the cycle, a slight recompression of the injected fuel—airmixture will occur. This recompression effect can be minimized andcompensated for by proper design of the engine cycle. Segment Ecorresponds to the combustion phase shown in FIGS. 3F and 4F. Segment Fcorresponds to the expansion portion of the cycle depicted in FIGS. 3Gand 4G. Optionally, segment G, indicates the exposure of optionalexhaust port 74C shown in FIGS. 3A-3H but omitted in FIGS. 4A-4H.

A timing diagram such as the diagram of FIG. 3 is not provided here toillustrate the operation of compression cylinder 13 as shown in FIGS.2A-2C. This is because the timing of the intake and compression portionsfor compression cylinder 13 is so simple that it can even be managedwith the use of spring loaded valves. However, the various processdescribed above can be related to thermodynamic diagrams FIG. 5 and FIG.6. Although, the present engine may a compression cycle that ismechanically separated from the combustion cycle, FIG. 5 and FIG. 6 showhow these separate mechanical cycles inter-relate in a singlethermodynamic cycle.

FIGS. 5 and 6 are thermodynamic plots of the type typically used bythose skilled in the art to diagram thermodynamic cycles. These plotspresent the state of the working fluid, which in this case is air,during the course of each cycle. The paths traced between points 1, 2, 3and 4 in FIGS. 5 and 6 represent the standard Otto cycle of a typicalprior art internal combustion engine. The paths traced between points 1,2A, 2B, 3A and 4A represent the thermodynamic cycle of the presentinternal combustion engine 10.

FIG. 5 is thermodynamic plots of pressure verses specific volume, whileFIG. 6 gives thermodynamic plots of temperature versus entropy. Specificvolume is merely the inverse of density and can be expressed in cubicmeters per kilogram. For many, entropy is a more difficult concept tograsp. It could be understood as the degree by which a working fluid(such as air in the present engine) deviates from the prevailingconditions of the surrounding environment. So, for example, in FIG. 6,state point 3A correlates to the end of the combustion process whengasses in combustion chamber 74B are very hot and at a very highpressure—a high entropy condition which differs greatly from ambientconditions. By contrast, state point 1 in FIG. 6 corresponds to ambientair prior to its intake in the compression stroke of compressioncylinder 13—a condition that does not differ from the low entropycondition of the surrounding environment.

As noted above, in FIG. 5 and FIG. 6, the thermodynamic cycle for atypical prior art Otto cycle engine is represented by a cycle thatfollows a path including state points 1, 2, 3 and 4. Compression occursbetween state points 1 and 2, combustion occurs between state points 2and 3, expansion of combustion gasses occurs between state points 3 and4 and the exhaust of the gaseous combustion products occurs betweenstate points 4 and 1. Generally, in a typical prior art engine,thermodynamic efficiency is understood as the ratio of the useful workcaptured between state points 3 and 4 and the energy input needed forcompression and fuel combustion occurring between state points 1 and 3.

In FIG. 5 and FIG. 6, the thermodynamic cycle for the preferredembodiment of present FIG. 1 engine is represented by the paths thattravel through state points 1, 2A, 2B, 3A and 4A. The compression ofcylinder 13 occurs between points 1 and 2A. The optional cooling ofcompressed air from cylinder 12 in compressed air conduit 50 occursbetween points 2A and 2B. Without this optional cooling, the processwould proceed from point 2A directly to point 3A. Note that in FIG. 6,state point 2B is at a temperature that is below the fuel ignitiontemperature. This permits spark controlled ignition as opposed toauto-ignition in an engine which uses a fuel adapted for spark ignition.Even though this cooling below the auto-ignition temperature results ina small energy loss, much of the thermodynamic benefit of the additionalcompression is retained. This additional compression corresponds to thepaths between points 2 to 2A in FIGS. 5 and 6.

For example, the state points 1, 2, 3 and 4 described above for atypical Otto cycle engine could be given as follows as shown in thechart below

Pressure (P) Sp. Vol. (v) Tempera- Point Description (MPa) (m³/kg) tureT (° K) 1 Start of 0.100 MPa 0.829 m³/kg 289° K Compression (14.4 psia)(60° F.) 2 End of Compression 1.825 MPa 0.104 m³/kg 663° K 3 End ofCombustion 8.739 MPa 0.104 m³/kg 3175° K 4 End of Exhaust 0.475 Mpa0.829 m³/kg 1382° K (69.0 psia) (2028° F.)The above chart describes an example process featuring a typical 8:1compression ratio where the heat added is 1900 KJ/Kg, heat loss is 783KJ/Kg and the useful work is 1017 KJ/Kg. This yields a thermodynamicefficiency of 56.5%.

In contrast, state points 1, 2, 2A, 2B, 3A and 4A shown in FIGS. 5 and6, could, for example, be described by the second chart below:

Pressure (P) Sp. Vol. (v) Tempera- Point Description (MPa) (m³/kg) tureT (° K) 1   Start of 0.100 MPa 0.829 m³/kg 289° K Compression (14.4psia) (60° F.) 2A End of Compression 6.597 MPa 0.041 m3/kg 957° K 2BIntercooler Exit 4.569 Mpa 0.041 m³/kg 663° K 3A End of Combustion21.878 MPa 0.041 m³/kg 3175° K 4A End of Exhaust 0.329 Mpa 0.829 m³/kg957° K (48.0 psia) (1264° F.)The above chart describes an example process which traces points 1, 2A,2B, 3A and 4A shown in FIGS. 5 and 6. This modified process features anenhanced 20:1 compression ratio achievable with the present engine. Inthis high compression process, the heat added is 1800 KJ/Kg, heat lossis 690 KJ/Kg and the useful work is 1010 KJ/Kg. This yields atheoretical thermodynamic efficiency of 61.7% which is significantlygreater than the theoretical 56.5% thermodynamic efficiency of theprocess given above having a typical 8:1 compression ratio.

Accordingly, presented here is an engine having a means for controllingthe pressure and temperature of compressed air in an Otto cycle and ameans for controlling the injection of compressed air into a combustioncylinder generally during the second half of a piston return stroke sothat higher thermodynamic efficiencies or power densities may beachieved.

It is to be understood that while certain forms of this invention havebeen illustrated and described, it is not limited thereto, except in sofar as such limitations are included in the following claims andallowable equivalents thereof.

1. A method for operating a two stroke cylinder engine, the methodincluding the steps of: (a) obtaining a two stroke cylinder of the typehaving a piston which reciprocates between top dead center and bottomdead center during a power stroke and between bottom dead center and topdead center during a return stroke, an intake valve and an exhaust valvefor opening communication between the inside of the cylinder and theoutside environment to exhaust combustion products from the cylinder andwherein the power stroke includes a first half which begins at top deadcenter and ends half way between top dead center and bottom dead centerand a second half which begins at half way between top dead center andbottom dead center and ends at bottom dead center, and wherein thereturn stroke includes a first half which begins at bottom dead centerand ends half way between bottom dead center and top dead center and asecond which begins at half way between bottom dead center and top deadcenter and ends at top dead center, (b) obtaining a source of compressedair including a compressor, a reservoir for receiving and storingcompressed air from the compressor, a hot conduit for conveying hotcompressed air from the reservoir and a cool conduit for conveyingcooled compressed air from the reservoir and a valve for combiningcompressed air from the hot conduit and the cool conduit to make acompressed air mixture having a temperature between the temperature ofthe air in the hot conduit and the temperature of the air in the coolconduit, (c) injecting the compressed air mixture and fuel into thecylinder during and the second half of the return stroke, (d) initiatingcombustion of the fuel air, (e) opening the exhaust valve after thecylinder has reached the second half of the power stroke to therebyexhaust the combustion products from the cylinder, (f) closing theexhaust valve after the commencement of the injection of the compressedair mixture and fuel into the cylinder.